A U.S. Public Health Service poster from the 1940s. Getty Images
In a twist of fate, there is new hope for developing a vaccine to protect people from the sexually transmitted disease gonorrhea, a disease eluding the medical community that has now become a sex superbug.
The vaccine, called MeNZB, was developed to control a meningitis epidemic in New Zealand from 2004 to 2006 and is no longer available. Researchers found that people vaccinated with the MeNZB were 31 percent less likely to get gonorrhea than those who weren't.
In the study, 1 million people who had been diagnosed with gonorrhea or chlamydia received the vaccine in a mass immunization program. Nearly 15,000 people were included in the analysis.
It's not clear yet how long the immune response from this vaccine might last, but this is an important breakthrough. According to the World Health Organization, there are about 78 million new cases of this STD worldwide each year. Around 400,000 Americans were diagnosed with gonorrhea in 2015.
Rise of a superbug
Over the past few decades, Neisseria gonorrhoeae, the bacterium that causes gonorrhea, has grown resistant to nearly every type of antibiotic used to treat it. That's bad news, because if gonorrhea is not treated, it can cause pain and fertility problems in both men and women; in pregnant women it can cause complications for mother and child alike. Now infection rates are rising, and public health experts think it's only a matter of time until a strain emerges that is completely resistant to all known antibiotics.
The Centers for Disease Control and Prevention lists N. gonorrhoeae among the three bacteria that are urgent drug-resistant threats to the United States, deserving of the highest concern.
Preventing infection in the first place seems to be the best option, "and the most proven, reliable and cost-effective method of prevention would be the implementation of an effective vaccine," according to a 2016 study. Though the bacteria's biology makes it a particularly difficult adversary, scientists are optimistic about their prospects. Several hope to get a gonorrhea vaccine into clinical trials within the next decade.
The challenges in creating such a vaccine are great. That's because N. gonorrhoeae quickly swaps genetic code with other bacteria with which it comes into contact, populating its surface with different proteins and effectively masking it to the host's immune system. All bacteria do this to some extent — that's how they're able to develop resistance — but N. gonorrhoeae does it much faster than others. That means gonorrhea is a disease you can get more than once.
Traditional approaches of vaccines, which work on the principle that dosing a patient with dead versions of the pathogen to train the immune system to recognize it in the future don't suffice. And because N. gonorrhoeae has evolved to only live in humans, it's challenging to test on animal models (there is a strain of genetically modified mice on which researchers currently experiment).
Scientists get creative
Armed with a few more decades of basic knowledge about how N. gonorrhoeae interacts with the body, plus more detailed DNA sequencing, researchers are applying creative new tactics to developing a vaccine. "What we found in our studies is that N. gonorrhoeae has the capacity to suppress the development of an immune response against it. This gives us an entirely new way of looking at the infection," says Michael Russell, a professor emeritus of microbiology and immunology, and oral biology at the Witebsky Center for Microbial Pathogenesis and Immunology at the University of Buffalo.
For the past several years, Russell and his collaborators have been developing a new kind of vaccine, based on a cancer treatment. It's designed to boost the immune response at the same time as the body is faced with inactive cells of N. gonorrhoeae, countering the bacteria's typical immunosuppressive mechanisms.
So far, mice have retained immunity for up to six months with this technique. Russell speculates that his lab could have a vaccine in clinical trials in the next five to 10 years, but there are some important questions to answer first. They want to better understand the mechanisms that make their vaccine successful, and make sure the immune response the technique elicits doesn't itself cause damage.
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Scott Gray-Owen, a professor of molecular genetics at the University of Toronto, has come up with another possible target for a vaccine. He and his collaborators have found a unique protein on the surface of N. gonorrhoeae that the bacteria uses to retrieve iron from its host. It's one of the few things that stay constant on the surface of N. gonorrhoeae, which makes it a good target for a vaccine, Owen says.
His team is now working on isolating the protein from a few different strains of N. gonorrhoeae and creating a proper adjuvant, the chemical in a vaccine that indicates to the immune system that something is hazardous. Because of how the vaccine works, they've been able to test it on pigs and cows, addressing other bacterial infections that bind to their cells the same way. "Economically, it's important for the health of these animals, but it's also exciting because it's a proof of concept," he says. He hopes to start clinical trials within a decade.
There are similar and related research efforts under way. Peter Rice and Sanjay Ram, at the University of Massachusetts Medical School, are testing a vaccine candidate of their own. Other researchers are working to better understand the bacteria's biology — Kate Sieb, a microbiologist at the Institute for Glycomics at Griffith University in Australia, is analyzing N. gonorrhoeae's genetic code to identify possible new targets for future vaccines.
"Given the high cost of clinical trial, it is likely that public–private partnerships will be required to drive development of a gonococcal vaccine."
Russell believes the work in his lab is the most mature and stands a good chance of being the first to the clinic. But to Gray-Owen, in practice the techniques would be complementary, perhaps providing immunity to different groups of people within the larger population.
Once a vaccine becomes available, there might be hurdles in getting people to use it. One element might be the delivery method — Russell's treatment is administered vaginally in the mouse models, and he thinks that probably wouldn't be acceptable in humans, "in part because it's not applicable in 50 percent of the population to start with," he says. There might be ethical issues to address, like if everyone should get it or only those at the highest risk, or if it's acceptable to put out a vaccine that only works on men or women but not both.
Parents also might be wary of vaccinating kids against a sexually transmitted infection, as was the case with the HPV vaccine, Gray-Owen says. "It might be difficult to convince parents that their young child should get a vaccine for gonorrhea. But as [the children] get older and start to realize the concern, if gonorrhea becomes untreatable or if the prevalence goes up in North America, I think that makes it not a crazy idea anymore," he says.
Researchers in this field are overwhelmingly optimistic. Whereas their work might have seemed Sisyphean or irrelevant in the past, a successful vaccine seems closer at hand than ever.
"There are a lot of potential vaccine targets that have been identified, and we really need to get data from human trials as soon as possible. Given the high cost of clinical trial, it is likely that public–private partnerships will be required to drive development of a gonococcal vaccine," says Seib of Griffith University.
"I think it's going to be possible. I can't tell you exactly when it will be, but I think the findings that have emerged from our lab and elsewhere in recent years have made it likely to be feasible. There's been a lot of pessimism around for many years, but I think the tide is beginning to turn," Russell says.
Given the current trend in gonorrhea infections and resistance, a vaccine like this could come just in time.
— By Alexandra Ossola, special to CNBC.com